New 4 mil melt down

[thomas h.]

We leak tested it and air is coming from opposite of the melted piston. New hotrods crank stock carbs 350 mains.

Friends bike could the labyrinth seal caused this melt down?

[98_shee]

The air leak could of caused it, it sounds like it was running lean. Post a few pics of the pistons.

[wacko2000]

Didn't HJR just build this?

Maybe you should contact him

[So Cal Suspension]

Didn't HJR just build this?

Maybe you should contact him

I was JUST thinking the same thing, but:

 

Friends bike could the labyrinth seal caused this melt down?

 

"Friends bike". I dunno

[Starwriter]

WTF???? Are you trying to pressure test just 1 cylinder? The labyrinth seal is just a block of aluminum with a hole bored in it. OK, there are actually some grooves in the bored hole, but there is no actual seal.

[thomas h.]

Not from HJR my friends bike pic is hard to do but deff not a cold seize. The labyrinth seal is sealing the sides right? There is a oring? Maybe pitched oring? We sprayed the crap out of it with soap& water. And used the motion pro tool set to find the leak it was hard to keep pressure going in to find the rapid leak but I moved the kicker and then we really heard it leaking out.

[thomas h.]

So is it a labyrinth seal or oil control or ? It got to be a seal because that would mess with vaccum

[gotta_goatsfast]

The o-ring is to keep the bearings from spinning... you cannot test one cylinder.

[Starwriter]

OK, I still don't understand what you're doing or WHERE you have air coming out, but, I can tell you this. The part that's called a labyrinth seal is the round chunk of aluminum in the middle of the crank. It does not actually seal. The steel center shaft of the crank just turns inside the bored aluminum hole. The vacuum/pressure pulses in the bottom end are happening so fast that there isn't a significant amount of transfer from side to side. You can not just pressure test 1 cylinder. The air will leak right through the labyrinth seal and out the open exhaust.

[thomas h.]

Ok I'll check both

[RadarRacing]

It is entirely possible to have one or more air leaks causing a lean down. Thats also why when yoy start a motor up you should look at the plugs before you ride it more than a small amount after proper heat cycles. Sorry to hear this and I hope you find your problem.

[camatv]

i listen to the motor. if its got a leak it wont come back to idle very quickly also. sure sign of lean/ leakage.

 

the lab seal has a grove cut in it and it gets some oil in and through it over time it kinda seals off the 2 sides like that but not much issue really

[edgehanger]

You say the leak is so rapid you can hear it? Well by it being so rapid you would have to stop that leak t=before you can find any other leaks. If it won't hold pressure at all that leak should be easy to find. Are you saying you can hear it but can't find it?

[thomas h.]

With the vaccume hooked up and one side plugged up we can hear air from the non melt down side spark plug hole ( with out plugs )

Still no pics

I guess we need to test with both side plugged up.

Also is pressurizing the motor ok under 10 lbs? Because vaccume about 5 lbs just doesn't make good bubbles

Thanks for the input guys

[thomas h.]

Does every one agree on what every one is saying?